The purpose of this work is to use gene fusions to study various aspects of ribosomal RNA and RNA polymerase genetics and control. The ability to fuse two different operons has provided an extra dimension to the techniques avaiable to the molecular geneticist for studying the regulation of genes that make products that are difficult to measure. Recombinant DNA technology greatly simplifies the assembly of genetic information from different sources in a highly controlled manner. We have constructed gene fusions of regulatory regions from ribosomal RNA, ribosomal protein and RNA polymerase genes with the beta-galactosidase gene. These fusions provide a way of studying and manipulating an isolated control element. A combination of in vivo physiological studies and genetic selection techniques, in vitro mechanism experiments and DNA sequencing methods can thus be applied to the study of specific control regions. We have used gene fusions to identify and pecisely locate promotors, attenuators, terminators and RNA processing sites. In addition they have been useful in studying the polar response elicited by nonsense mutations in some genes.